On Mon, Oct 27, 2008 at 03:34:14PM +0800, Zhao, Yu wrote: > >Erm, no, the 'dev' cannot be destroyed because the caller has a refcount > >on it. The physical device backing it might have gone away. The dev > > Why does the caller have a reference count? I don't see we increase the > reference count after the 'dev' is returned by following in > pci_get_dev_by_id(): > > dev = bus_find_device(&pci_bus_type, dev_start, (void *)id, > match_pci_dev_by_id); > > And this 'dev' becomes the 'from' in the next loop, but it may be > destroyed before the 'pci_dev_get(from)', isn't it? Either you've gone back to talking about pci_find_device() [which, yes, is vulnerable to race conditions, we know that, it's not interesting to talk about it], or you're refusing to take it on faith that pci_get_dev_by_id() returns a device with an increased refcount. And if you don't believe that is true, please follow the code in bus_find_device() to prove it. -- Matthew Wilcox Intel Open Source Technology Centre "Bill, look, we understand that you're interested in selling us this operating system, but compare it to ours. We can't possibly take such a retrograde step." -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
